Among field brown dwarfs methane appears—by definition—at the L to T-type transition where their near-infrared colors turn to the blue at effective temperatures near 1200 K [1]}. The first directly imaged planets, however, were found to have effective temperatures below 1200 K and yet their near-infrared spectra were devoid of signs of methane in K band [2]}.
The best example is HR8799c: despite an effective temperature near 1100 K, in both low and high resolution spectra—particularly the high resolution spectrum taken by [3]}—methane has gone missing.
